The disclosures herein relate generally to total knee replacement and more particularly to an automatic clamp for an alignment guide used in resecting the tibial plateau.
During total knee surgery, the proximal portion of the tibia is cut away in preparation for a tibia implant. A cutting block or guide is typically used to aid the surgeon in locating and making the cut. Placement of the tibia cutting block is critical to establishing the plane of the tibial plateau for providing the proper alignment of the implant. One device commonly used for achieving property alignment is an extramedullary alignment assembly including an elongated rod. The distal end of the rod is connected to an ankle clamp used to stabilize the rod in order to assist in establishing the correct angle of cut for the tibial plateau.
Several known devices are used for this purpose. One such device includes a cradle that provides a "V" shaped notch for receiving the ankle. In this device the surgeon or an assistant must hold the ankle cradle in place during alignment.
In another known device, a "V" shaped cradle is held in place by a strap or a tension spring which wraps around the ankle and fastens to the cradle. This device securely holds the clamp in place after alignment is established. However, two hands are required to position the device during alignment.
U.S. Pat. No. 5,628,750 discloses a tibial resection guide alignment device including an extramedullary mount having a separate extramedullary member which may be removably mounted to a base member. A bottom assembly is connected to the extramedullary member by which the device may be connected around a patient's lower leg or ankle. A "V" shaped cradle includes two spring loaded arms that close around the ankle for stability and require the use of two hands for operation.
In U.S. Pat. No. 5,197,944, an ankle clamp apparatus for use in tibial cutting instruments has a frame with pivoting arms attached for gripping a patient's ankle during use. The arms can be held open with latches prior to placement and quickly released to grip the patient's leg by depressing the latches. A "V" shaped cradle includes spring loaded arms. The arms may be locked in an open position and released to a closed position in response to depressing an individual button for each arm. Although this device purports to be for single handed operation, it requires each button to be separately depressed for releasing a respective arm. Therefore, in order to release both arms simultaneously, both buttons must be depressed simultaneously, which requires two handed operation.
Single handed use is very desirable during surgery. A probable limitation with the individual buttons for releasing the arms is the inability to simultaneously reach both buttons with the same hand that is positioning the clamp, therefore negating the single handed use. Another problem might be the accidental misalignment of the clamp. When only one arm closes from one side, the cradle may shift to the opposite side that is not yet being held. Again, this may require the use of a second hand to maintain alignment during clamping.
Therefore, what is needed is a clamping device which attaches to the alignment rod and which automatically clamps onto the patient's ankle when engaged therewith such that the surgeon's hands remain free to stabilize the extramedullary alignment assembly and cutting block.